Recording medium, recording method, recording/reproducing apparatus, and cutting apparatus

ABSTRACT

A recording medium such as an optical or magneto-optical disk divided into servo areas and data areas, wherein at least one of pits in each servo area is formed with a phase deviation. There are also disclosed a method of recording pits on such a recording medium, and an apparatus for recording data on and/or reproducing the same from the recording medium. The apparatus comprises a light source for irradiating a light output to the recording medium; a photoelectric conversion circuit for receiving the light emitted from the light source and reflected from or transmitted through the recording medium, and converting the received light into an RF signal; a signal conversion circuit for converting the output RF signal of the photoelectric conversion circuit into a binary signal corresponding to the pit formed on the recording medium; and a detection circuit for detecting the servo area on the recording medium on the basis of the phase deviation of the binary signal outputted from the signal conversion circuit; wherein data is recorded or reproduced while a servo action is executed in accordance with the servo byte in the servo area detected by the detection circuit. The servo area is detectable with facility, and data of any pit pattern can be recorded and/or reproduced properly.

This is a continuation, of application Ser. No. 08/430,183, filed Apr.27, 1995 now abandoned which is a continuation of Ser. No. 08/118,636,filed Sep. 10, 1993 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording medium adapted for use asan optical disk, a magneto-optical disk or the like, and also to amethod of recording data on such a recording medium, an apparatus forrecording data on and/or reproducing the same from the recording medium,and further to an apparatus for cutting the recording medium.

2. Description of the Related Art

On an optical disk (ROM disk) or the like where tracking is executed bya sample servo system, a multiplicity of servo areas are formed atpredetermined intervals on tracks together with data areas for recordingordinary data, wherein each of the servo areas includes wobbled pits foreffecting a tracking servo action, a mirror portion for effecting afocus servo action, and a clock pit for generating a clock signal (foreffecting a spindle servo action to a spindle motor for rotating theoptical disk).

Meanwhile in an optical disk apparatus for reproducing the recorded datain the data areas on the optical disk, such servo areas (servo bytes)formed on the optical disk are detected and used for tracking orgeneration of a clock signal.

For the purpose of enabling the optical disk apparatus to exactly detectthe servo area, it has been necessary heretofore to modulate the data,which is recorded in the data area on the optical disk mentioned above,in such a manner that the pit pattern thereof becomes different from thepit pattern of servo bytes composed of wobbled pits and clock pits inthe servo area. More specifically, if nonmodulated data is recorded onthe optical disk, there may arise a problem that the servo byte patternin the servo area on the optical disk fails to become a unique pattern,whereby the servo area (servo byte) on the optical disk is renderedundetectable.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of the circumstancesmentioned above. And its object is to provide an improvement whichrealizes proper detection of servo bytes with facility and is capable ofrecording and/or reproducing data of any pattern.

According to a first aspect of the present invention defined in theappended claim 1, there is provided a recording medium divided intoservo areas and data areas, wherein at least one of pits in each servoarea is formed with a phase deviation.

According to a second aspect of the present invention defined in theappended claim 6, there is provided a method of recording pits on arecording medium divided into servo areas and data areas, And itsfeature resides in forming at least one of the pits in each servo areawith a phase deviation.

According to a third aspect of the present invention defined in theappended claim 7, there is provided a recording/reproducing apparatuswhich comprises a laser diode as a light source for irradiating itsoutput light to a recording medium such as an optical disk where atleast one of pits in each servo area is formed with a phase deviation; alight receiving element as a photoelectric conversion means forreceiving the light emitted from the laser diode and reflected from ortransmitted through the optical disk, and converting the received lightinto an RF signal; a peak detection circuit as a signal conversion meansfor converting the output RF signal of the light receiving element to abinary signal corresponding to the pit formed on the optical disk; and aunique pattern detector as a servo area detection means for detectingthe servo area on the optical disk in response to the phase deviation ofthe binary signal outputted from the peak detection circuit; wherein thedata is recorded and/or reproduced while a servo action is executed onthe basis of the servo byte in the servo area detected by the uniquepattern detector.

And according to a fourth aspect of the present invention defined in theappended claim 8, there is provided an apparatus for cutting a recordingmedium divided into servo areas and data areas, wherein at least one ofpits in each servo area is formed with a phase deviation.

On the recording medium of the appended claim 1, at least one of thepits in each servo area is formed with a phase deviation, so that theservo area can be detected by detection of the phase deviation in thedata reproduced from the recording medium. And it is possible to recorddata of any pit pattern on such recording medium.

In the recording method of the appended claim 6, at least one of thepits in each servo area is formed with a phase deviation on therecording medium. Therefore the servo area is rendered detectable bydetecting such phase deviation of the data reproduced from the recordingmedium.

In the recording/reproducing apparatus of the appended claim 7, light isirradiated to a recording medium such as an optical disk where at leastone of the pits in each servo area is formed with a phase deviation, andthe light reflected from or transmitted through the recording medium isreceived and converted into an RF signal. Then such RF signal is furtherconverted to a binary signal corresponding to the pit formed on theoptical disk, and the servo area on the optical disk is detected on thebasis of the phase deviation of the binary signal. And the data isrecorded or reproduced while a servo action is executed in conformitywith the servo byte in the detected servo area. Consequently the servoarea is detectable with facility.

And in the cutting apparatus of the appended claim 8, at least one ofthe pits in each servo area is formed with a phase deviation on arecording medium such as an optical disk. Therefore it becomes possibleto easily detect the servo area on such a recording medium.

The above and other features and advantages of the present inventionwill become apparent from the following description which will be givenwith reference to the illustrative accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the constitution of an exemplaryoptical disk apparatus where the recording/reproducing apparatus of thepresent invention is applied;

FIG. 2(a) to FIG. 2(h) is a waveform chart of signals outputtedrespectively from the blocks of the apparatus shown in FIG. 1;

FIG. 3 is a detailed block diagram of a unique pattern detector employedin the apparatus of FIG. 1 and

FIG. 4 is a block diagram of an exemplary embodiment representing thecutting apparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram showing the constitution of an exemplaryoptical disk apparatus where the recording/reproducing apparatus of thepresent invention is applied. An optical disk 1 used therein consists ofthe recording medium of the present invention, on which each of tracksis composed of a plurality of sectors, and each sector is composed of aplurality of segments. Each segment is divided into a servo area havinga servo byte (servo pits) and a data area for recording essential data.And at least one of the pits in each servo area is formed with a phasedeviation of π for example.

In an exemplary case of using a clock signal (FIG. 2(b)) of a period 2T,data is recorded, in one data area on the optical disk 1, at a positioncorresponding in timing to the rise edge of the clock pulse of theperiod 2T. Then, in a servo area relative thereto, as shown in FIG.2(c), a clock pit in a servo byte composed of wobbled pits and suchclock pit is formed at the position corresponding in timing to the falledge of the clock pulse of the period 2T (FIG. 2(b)).

A spindle motor 2 rotates the optical disk 1 at a predetermined velocityin accordance with a spindle servo signal obtained from a servo circuit14. A laser diode 3 is a light source for irradiating a laser lightoutput to the optical disk 1. A collimator lens 4 serves to collimatethe laser light beam emitted from the laser diode 3. And a beam splitter5 causes the output light of the collimator lens 4 to be incident on anobjective lens 6 while reflecting, by means of an incorporated halfmirror, the light reflected from the optical disk 1 via the objectivelens 6, thereby causing the reflected light to be incident on acondenser lens 7.

The objective lens 6 is driven in response to a tracking servo signal ora focus servo signal outputted from a servo circuit 14 and focuses, onthe optical disk 1, the laser light irradiated thereto from the laserdiode 3 via the collimator lens 4 and the beam splitter 5. Meanwhile thecondenser lens 7 focuses, on the surface of the light receiving element8, the light reflected from the optical disk 1 and incident on thecondenser lens 7 via the objective lens 6 and the beam splitter 5.

The light receiving element 8 receives the reflected light from theoptical disk 1 and transmits to a head amplifier 9 an output RF signal(FIG. 2(d)) equivalent to the amount of the received light. Then thehead amplifier 9 amplifies the RF signal obtained from the lightreceiving element 8 and supplies the amplified signal to both a peakdetection circuit 10 and a servo circuit 14.

The peak detection circuit 10 converts the RF signal (FIG. 2(d))obtained from the light receiving element 8 via the head amplifier 9, toa binary signal (FIG. 2(e)) corresponding to the pit formed on theoptical disk 1. More specifically, the peak detection circuit 10 detectsthe peak value of the RF signal (FIG. 2(d)) outputted from the lightreceiving element 8 via the head amplifier 9 and, after producing apulse (FIG. 2(e)) corresponding to the detected peak value, suppliessuch pulse to both a PLL circuit 11 and a unique pattern detector 12.

The PLL circuit 11 produces a double-frequency clock signal (FIG. 2(a))of a period T, which is half the recording period 2T relative to thedata in the data area on the optical disk 1, out of the binary signalobtained from the peak detection circuit 10, and then supplies thedouble-frequency clock signal of the period T to both the unique patterndetector 12 and a timing generator 13.

The unique pattern detector 12 comprises a delay circuit 21 and an ANDgate 22 as shown in FIG. 3. The delay circuit 21 delays the outputbinary signal of the peak detection circuit 10 by a time lengthequivalent to an odd multiple of the period T of the double-frequencyclock signal (FIG. 2(a)) supplied from the PLL circuit 11, and thenfeeds the delayed signal to one input terminal of the AND gate 22. Morespecifically, the delay circuit 21 delays the output binary signal ofthe peak detector 10 by a time length of (2n+1)T and feeds the delayedsignal to one input terminal of the AND gate 22. In (2n+1)T mentionedabove, n=0, 1, . . . and so forth; and n=1 in this embodiment. Itfollows therefore that the delay circuit 21 in this embodiment delaysthe binary signal by a time length of 3T. Although n may be set to anydesired value, it is preferred that n be set in conformity with theperiod (interval) of the pits formed on the optical disk 1.

The AND gate 22 delivers a logic product of the binary signal suppliedto its one input terminal from the delay circuit 21 with a delay of(2n+1)T and another binary signal supplied to the other input terminalfrom the peak detection circuit 10, and transmits a high-level orlow-level output to the timing generator 13.

The servo circuit 14 receives the RF signal from the head amplifier 9 inresponse to a control signal (FIG. 2(h)) outputted from the timinggenerator 13, and transmits an output servo signal to the spindle motor2 or the objective lens 6 in accordance with such RF signal (whichcorresponds to the servo area on the optical disk 1 as will be mentionedlater).

Now the operation of the above apparatus will be described below. Whenthe power supply is switched on for the apparatus, the spindle motor 2rotates the optical disk 1 where the clock pit (FIG. 2(c)) out of thepits in the servo area is formed with a phase deviation π, andsimultaneously a laser light output is irradiated from the laser diode 3to the optical disk 1 via the collimator lens 4 and the beam splitter 5.The laser light irradiated to the optical disk 1 is reflected therefromand then is incident on the surface of the light receiving element 8 viathe objective lens 6, the beam splitter 5 and the condenser lens 7. Thusthe reflected light from the optical disk 1 is received by the lightreceiving element 8, and an RF signal (FIG. 2(d)) equivalent to theamount of the received light is supplied via the head amplifier 9 toboth the peak detection circuit 10 and the servo circuit 14.

In the peak detection circuit 10, the RF signal (FIG. 2(d)) outputtedfrom the light receiving element 8 via the head amplifier 9 is convertedto a binary signal (FIG. 2(e)) corresponding to the pit formed on theoptical disk 1, and such binary signal is supplied to both the PLLcircuit 11 and the unique pattern detector 12.

In the PLL circuit 11, a double-frequency clock signal (FIG. 2(a)) of aperiod T, which is half the recording period 2T relative to the data inthe data area on the optical disk 1, is produced out of the binarysignal (FIG. 2(e)) obtained from the peak detection circuit 10, and thensuch double-frequency clock signal is supplied to both the uniquepattern detector 12 and the timing generator 13.

In the delay circuit 12 of the unique pattern detector 12, the binarysignal outputted from the peak detection circuit 10 is delayed by a timelength of, e.g., 3T which is an odd multiple of the period T of thedouble-frequency clock signal (FIG. 2(a)) supplied from the PLL circuit11, and the delayed signal is fed to one input terminal of the AND gate22. In the AND gate 22, there is delivered a logic product of the binarysignal (FIG. 2(f)) supplied to its one input terminal from the delaycircuit 21 with a delay of 3T and another binary signal (FIG. 2(e))supplied to the other input terminal from the peak detection circuit 10,and then a high-level or low-level output (FIG. 2(g)) is transmitted tothe timing generator 13.

In an exemplary case of using the clock signal (FIG. 2(b)) of a period2T as described, data is recorded, in one data area on the optical disk1, at a position corresponding in timing to the rise edge of the clockpulse of the period 2T. Then, in a servo area relative thereto, as shownin FIG. 2(c), a clock pit in a servo byte composed of wobbled pits andsuch clock pit is formed at the position corresponding in timing to thefall edge of the clock pulse of the period 2T (FIG. 2(b)).

More specifically, in the use of the double-frequency clock signalproduced by the PLL circuit 11 and consisting of pulses C1, C2, C3, . .. and so forth (FIG. 2(a)) of a period T which is half the recordingperiod 2T relative to the data in the data area on the optical disk 1,the pit (FIG. 2(c)) in the data area is formed at the positioncorresponding to an odd pulse (e.g., C11 or C13 in FIG. 2) of thedouble-frequency clock signal. Then it follows that the clock pit (FIG.2(c)) in the servo area is formed at the position corresponding to aneven pulse (e.g., C4 in FIG. 2) of the double-frequency clock signal.

Consequently, in the AND gate 22 (FIG. 3) of the unique pattern detector12, there is delivered a logic product of the binary signal (FIG. 2(e))converted from the RF signal (FIG. 2(d)) and the binary signal (FIG.2(f)) delayed by a time length of 3T in the delay circuit 21.Subsequently, as shown in FIG. 2(g), a high-level output is transmittedfrom the AND gate 22 to the timing generator 13 in synchronism with thepulses C4 and C7 of the double-frequency clock signal (FIG. 2(a)), i.e.,in synchronism with reproduction of the RF signal corresponding to thereflected light from the vicinity of the servo byte formed on theoptical disk 1.

The operation mentioned above is performed repeatedly until a high-leveloutput is transmitted from the unique pattern detector 12 at thepredetermined timing. Then, in the timing generator 13, a control signal(a window corresponding to the interval of the segments on the opticaldisk 1) (FIG. 2(h)) is outputted to the servo circuit 14 approximatelyat the above-described predetermined timing, i.e., in synchronism withreproduction of the RF signal corresponding to the reflected light fromthe vicinity of the servo byte formed on the optical disk 1, in such amanner as to receive the RF signal from the head amplifier 9.

The RF signal obtained from the head amplifier 9, i.e., the RF signalcorresponding to the reflected light from the servo byte (servo area)formed on the optical disk 1, is inputted to the servo circuit 14 inresponse to a control signal (FIG. 2(h)) outputted from the timinggenerator 13, and a servo signal is transmitted from the servo circuit14 to the spindle motor 2 or the objective lens 6 in accordance withsuch RF signal corresponding to the reflected light from the servo byte(servo area) on the optical disk 1.

Subsequently the spindle servo, tracking servo and focusing servoactions are executed and, in a play-back circuit (not shown), the datais reproduced from the RF signal outputted from the head amplifier 9.

As described above, first the RF signal is converted to a binary signalcorresponding to the pit formed on the optical disk 1, and the servobyte on the optical disk 1 is detected on the basis of the phasedeviation of the binary signal thus obtained, so that it becomespossible to detect the servo byte with facility even if data of any pitpattern such as nonmodulated one is recorded on the optical disk 1.

The optical disk 1 mentioned above may be replaced with amagneto-optical disk and, if the apparatus shown in FIG. 1 is furtherequipped with a circuit for detecting an optical deflection, a magnetichead for applying a magnetic field, and a recording circuit forconverting record data into light, then it can function as amagneto-optical disk apparatus for recording data on and/or reproducingthe same from a magneto-optical disk.

FIG. 4 is a block diagram showing the constitution of an exemplaryembodiment which represents the cutting apparatus of the presentinvention. In this apparatus, a glass substrate 31 is coated with aphotoresist (hatched in the drawing), and data is recorded by exposureof such photoresist to a laser light beam. A laser light source 32irradiates its laser light output onto the glass substrate 31 via anacoustic optical modulator (AOM) 33a, an acoustic optical deflector(AOD) 33b, a prism 34 and an objective lens 35.

The AOM 33a is controlled by a driver circuit 39 and switches on or offthe laser light emitted from the laser light source 32. Morespecifically, the AOM 33a passes or intercepts the light being emittedfrom the laser light source 32 to the glass substrate 31 via the AOD33b, the prism 34 and the objective lens 35. The AOD 33b deflects thelaser light, which is irradiated from the laser light source 32 via theAOM 33a, in accordance with control of the driver circuit 39. The prism34 reflects, toward the objective lens 35, the laser light irradiatedfrom the laser light source 32 via the AOM 33a and the AOD 33b. And theobjective lens 35 is controlled by a servo controller 41 and focuses thelaser light, which is reflected by the prism 34, onto the photoresistsurface of the glass substrate 31.

Similarly to the aforementioned PLL circuit 11 in the optical diskapparatus of FIG. 1, a clock generator 37 generates a double-frequencyclock signal (FIG. 2(a)) of a period T and supplies the clock signal toboth a logic calculator 38 and a system controller 40. The systemcontroller 40 controls a formatting circuit 36, the driver circuit 39,the servo controller 41 or a slide motor 42 in response to thedouble-frequency clock signal obtained from the clock generator 37. Andthe servo controller 41 rotates the motor 43 at a predetermined constantangular velocity in accordance with control of the system controller 40while rotating the slide motor 42 to slide the glass substrate 31 in itsradial direction (e.g., the direction indicated by an arrow A in thedrawing). A frequency generator (FG) 44 generates FG pulses fordetecting the rotation velocity of the motor 43 and supplies such pulsesto the system controller 40.

The system controller 40 controls the servo controller 41, whichcontrols the rotation of the motor 43, in response to the FG pulsesobtained from the FG 44.

The motor 43 is controlled by the servo controller 41 to rotate theglass substrate 31 at a predetermined constant angular velocity. And amechanical unit 45 is driven by the slide motor 42 to slide the glasssubstrate 31 in its radial direction.

The formatting circuit 36 executes a process of adding an errorcorrection code or the like to the source data inputted thereto, andthen supplies the processed data to the logic calculator 38. The logiccalculator 38 incorporates a memory (not shown) of a required capacityand temporarily stores therein the data outputted from the formattingcircuit 36. The logic calculator 38 further executes a predeterminedlogic calculation of the data stored temporarily in the incorporatedmemory in response to the double-frequency clock signal obtained fromthe clock generator 37, thereby producing record data. The record datathus produced in the logic calculator 38 is supplied to the drivercircuit 39, which then controls the acoustic optical modulator (AOM) 33aor the acoustic optical deflector (AOD) 33b on the basis of such recorddata.

In the cutting apparatus mentioned, first the servo controller 41supplies a control signal to the motor 43 for rotating the glasssubstrate 31 at a predetermined constant angular velocity, and alsosupplies another control signal to the slide motor 42 for driving themechanical unit 45 so as to slide the glass substrate 31 in its radialdirection.

The glass substrate 31 is rotated by the motor 43 at a predeterminedconstant angular velocity in accordance with the control signal obtainedfrom the servo controller 41, and simultaneously the mechanical unit 45is driven by the slide motor 42 so that the glass substrate 31 is slidat a predetermined pitch in its radial direction per rotation thereof bythe motor 43.

The predetermined pitch is equivalent to the track pitch on the opticaldisk to be manufactured by the use of such glass substrate 31.

Simultaneously laser light is emitted from the laser light source 32 andthen is irradiated to the photoresist surface of the glass substrate 31via the AOM 33a, the AOD 33b, the prism 34 and the objective lens 35,whereby the photoresist surface is exposed.

Meanwhile in the formatting circuit 36, a process of adding an errorcorrection code or the like to the input source data is executed, andthe processed data is outputted to the logic calculator 38. Subsequentlythe data outputted from the formatting circuit 36 is temporarily storedin the memory incorporated in the logic calculator 38, where apredetermined logic calculation is executed for the stored data tothereby produce record data. And in the driver circuit 39, the AOM 33aor the AOD 33b is controlled, in response to the double-frequency clocksignal (FIG. 2(a)) supplied from the clock generator 37 via the systemcontroller 40, on the basis of the record data produced in the logiccalculator 38.

When the record data corresponds to, for example, the pit in the dataarea formed on the optical disk 1 to be reproduced by the optical diskapparatus of FIG. 1, the AOM 33a is so controlled by the driver circuit39 as to switch on or off the laser light being irradiated from thelaser source 32, on the basis of such record data in synchronism with,e.g., an odd pulse out of the entire odd pulses (C1, C3, . . . ) andeven pulses (C2, C4, . . . ) of the double-frequency clock signal (FIG.2(a)) outputted from the clock generator 37.In this case, the AOM 33a isso controlled as to switch off the laser light being irradiated from thelaser source 32, in synchronism with the even pulse of thedouble-frequency clock signal (FIG. 2(a)) out-putted from the clockgenerator 37.

In case the record data thus produced corresponds to the wobbled pit(FIG. 2(c)) in the servo byte formed on the optical disk 1 (FIG. 1), thedriver circuit 39 controls the AOM 33a in such a manner as to switch onthe laser light being irradiated from the laser light source 32, insynchronism with, e.g., an odd pulse (C1 or C7 in FIG. 2) out of theentire odd and even pulses of the double-frequency clock signal (FIG.2(a)) outputted from the clock generator 37. And simultaneously the AOD33b is so controlled as to deflect the laser light irradiated from thelaser light source via the AOM 33a.

Consequently, an exposed portion corresponding to the wobbled pit (FIG.2(c)) is formed on the glass substrate 31 in synchronism with the oddpulse of the double-frequency clock signal (FIG. 2(a)) outputted fromthe clock generator 37, with a radial deviation of a predetermineddistance from the tracking center in the servo byte on the optical disk1.

In another case where the record data corresponds to the clock pit (FIG.2(c)) in the servo byte formed on the optical disk 1 (FIG. 1), thedriver circuit 39 controls the AOM 33a in such a manner as to switch onthe laser light being irradiated from the laser light source 32, insynchronism with, e.g., the even pulse (C4 in FIG. 2) out of the entireodd and even pulses of the double-frequency clock signal (FIG. 2(a))outputted from the clock generator 37.

Consequently, an exposed portion corresponding to the clock pit (FIG.2(c)) in the servo byte on the optical disk 1 is formed on the glasssubstrate 31 in synchronism with the even pulse of the double-frequencyclock signal (FIG. 2(a)) outputted from the clock generator 37.

Thus an exposed portion corresponding to the clock pit, which is atleast one of the pits in the servo area, is formed on the glasssubstrate 31 with a phase deviation of π (180°).

Thereafter required processes such as developing and electroforming areexecuted for the glass substrate 31 where the exposed and nonexposedportions are formed as described, so that a metallic stamper ismanufactured. And a multiplicity of the optical disks 1 mentioned aboveare mass-produced by the use of such a stamper.

Although a description has been given herein-above with regard to anexemplary case of using an optical disk, it is to be understood that therecording medium of the present invention is not limited to the opticaldisk alone, and the invention is applicable also to any other opticalrecording medium such as a magneto-optical disk.

In the embodiments mentioned, merely the clock pit out of the entirepits in each servo area is formed with a phase deviation on the opticaldisk 1. However, any other pit such as a wobbled pit in the servo areamay be formed with a phase deviation on the optical disk 1. And thenumber of the phase-deviated pits on the optical disk 1 is not limitedto any particular value alone.

It is further to be understood that, although the phase of one pit(clock pit in the embodiment) in the servo area is deviated by π, thephase deviation of the pit is not limited merely to π alone.

As described hereinabove, according to the recording medium of thepresent invention where at least one of the pits in each servo area isformed with a phase deviation, the servo area can be detected bydetecting the phase deviation of the data reproduced from the recordingmedium. And data of any pit pattern is rendered recordable on therecording medium.

According to the recording method of the invention which forms at leastone of the pits in each servo area with a phase deviation, it becomespossible to detect the servo area by detecting the phase deviation ofthe data reproduced from the recording medium.

According to the recording/reproducing apparatus of the invention, lightis irradiated to the recording medium where at least one of the pits ineach servo area is formed with a phase deviation, and the lightreflected from or transmitted through the recording medium is receivedand converted into an RF signal. Thereafter the RF signal thus obtainedis further converted to a binary signal corresponding to the pit formedon the recording medium, and the servo area on the recording medium isdetected on the basis of the phase deviation of the binary signal, anddata is recorded or reproduced while a servo action is executed inaccordance with the servo byte in the detected servo area, whereby theservo area is detectable with facility.

And further according to the cutting apparatus of the invention, atleast one of the pits in each servo area is formed with a phasedeviation on the recording medium. Consequently it becomes possible toeasily detect the servo area from the recording medium.

What is claimed is:
 1. An apparatus for cutting a recording mediumhaving a recording track divided into servo areas having a plurality ofpits longitudinally arranged substantially collinearly along a centerline of the recording track and data areas immediately following saidservo areas, respectively, wherein at least one of said plurality ofpits in each servo area is formed with a phase deviation on saidrecording medium to enable detection of the servo areas, said apparatuscomprising:means for irradiating a glass substrate having a photo-resistsurface, the means for irradiating generating a light beam arranged toimpinge upon an acoustic optical modulator AOM, an acoustic opticaldeflector AOD, a prism and an objective lens; a driver circuit tocontrol said AOM to thereby switch on or off the means for irradiating;a servo controller to control the objective lens to thereby focus saidlight beam which is reflected by said prism onto said photo-resistsurface of said glass substrate; means for rotating said glass substrateat a predetermined constant angular velocity controlled by said servocontroller; means for sliding said glass substrate in a radial directioncontrolled by said servo controller; a clock generator to generate adouble frequency clock signal; a logic calculator constructed andarranged to receive said clock signal from said clock generator; and asystem controller to control a formatting circuit, said driver circuit,and said servo controller in response to said double frequency clocksignal obtained from said clock generator wherein said formattingcircuit processes input source data to supply an output of processeddata to said logic calculator such that said logic calculator producesrecord data to said driver circuit to control said AOM such that saidAOM or said AOD, dependent on said record data, controls said means forirradiating in synchronism with said double frequency clock signaloutput from said clock generator in conjunction with said servocontroller controlling said means for rotating and said means forsliding said glass substrate such that said light beam irradiates saidphoto-resist surface of said glass substrate, whereby the photo-resistsurface is exposed.
 2. A method for cutting a recording medium having arecording track divided into servo areas having a plurality of pitslongitudinally arranged substantially collinearly along a center line ofthe recording track and data areas immediately following said servoareas, said data areas having data pits at a predetermined clockfrequency respectively, wherein at least one of said plurality pits ineach servo area is formed with a phase deviation from said clockfrequency on said recording medium to enable detection of the servoareas, said method comprising the steps of:irradiating a glass substratehaving a photo-resist surface by generating a light beam arranged toimpinge upon an acoustic optical modulator AOM, an acoustic opticaldeflector AOD, a prism and an objective lens; controlling said AOM usinga driver circuit to thereby switch on or off the irradiating; using aservo controller to control the objective lens to thereby focus saidlight beam which is reflected by said prism onto said photo-resistsurface of said glass substrate; rotating said glass substrate at apredetermined constant angular velocity controlled by said servocontroller; sliding said glass substrate in a radial directioncontrolled by said servo controller; generating a double frequency clocksignal; using a logic calculator constructed and arranged to receivesaid clock signal; and providing a system controller to control aformatting circuit, said driver circuit, and said servo controller inresponse to said double frequency clock signal wherein said formattingcircuit processes input source data to supply an output of processeddata to said logic calculator such that said logic calculator producesrecord data to said driver circuit to control said AOM such that saidAOM or said AOD, dependent on said record data controls said irradiatingin synchronism with said double frequency clock signal output inconjunction with said servo controller controlling said rotating andsaid sliding of said glass substrate such that said light beamirradiates said photo-resist surface of said glass substrate to exposethe photo-resist surface.
 3. The method according to claim 2, whereinsaid logic calculator and said driver circuit control said AOM to exposesaid photo-resist surface to create said at least one of said pluralityof pits in each servo area to include two wobbling pits formed in phasewith said predetermined clock frequency, and a clock pit formed with aphase deviation π between said clock pit and said predetermined clockfrequency.